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Abstract:

A variable orifice fuel injector has both an inward opening needle valve
and an outward opening needle valve and has means to inject dual fuels in
different hollow conical spray patterns and conventional multiple jet
spray patterns selectively and independently.

Claims:

1. A variable orifice fuel injector comprising: (i) a nozzle body (3)
comprising passages for pressured fuel, an inner cylindrical bore (307)
for receiving two longitudinally displaceable coaxial needle valves (1,2)
with an outward opening inner needle valve (1) which is moving away
relative to nozzle body large end (306) to reach opening position, and an
inward opening outer needle valve (2) which is moving toward nozzle body
large end to reach opening position, fuel outlets (302) in said nozzle
body, and two seal surfaces on said nozzle body with a seal surface (231)
which provides sealing for said inward opening needle valve (2) to block
fuel, and another seal surface (131) which provides sealing for said
outward opening needle valve (1) and guidance for fuel path, at least one
spring (5) which urges said two coaxial needle valves (1,2) into biased
seating positions to block fuel, and a valve block (8) to hold control
valves, and (ii) said outward opening needle valve (1) which has means to
inject fuel into combustion chamber in a hollow conical spray pattern
through annular fuel outlet (131') when it is displaced from seating
position to opening positions, and (iii) said inward opening needle valve
(2) which has means to inject fuel into combustion chamber in
conventional multiple jet spray patterns through fuel outlets (302) when
it is lifted from seating position to opening positions; Where in, said
variable orifice fuel injector has means to inject different fuels in
different hollow conical spray patterns and conventional multiple jet
spray patterns selectively and independently.

2. A fuel injector of claim 1, where in it is comprising at least two
valves (9, 10, 11) to block or flow at least one type of fuel from high
pressure fuel reservoirs (12, 13) to low pressure fuel sink (15, 15') to
produce the lifting and closing forces on said needle valves (1,2)
through generating pressure differences in pressure control chambers
(381, 681', 261', 234), where in two of the control valves (10,11) have
opposite opening-closing states and can be served with a single actuator
to control the longitudinal displacement and closing of said outward
opening needle valve (1), and another control valve (9) is served with a
separate actuator to control the lifting and closing movement of said
inward opening needle valve (2), where in said inward and outward opening
needle valves (1,2) have the same maximum needle lift (H).

3. A fuel injector of claim 1, where in said outward opening needle valve
(1) is longitudinally displaceable and partially contained within said
inward opening needle valve (2) and guided by said needle guide (6) which
is longitudinally displaceable in the inner bore (307) of said nozzle
body (3), and said outward opening needle valve (1) has a partially tube
section (106) to supply fuel and an arrow-head shape needle head (101)
for guiding a hollow conical spray of fuel, wherein said needle valve (1)
is at a biased closing position, or at an opening position through
pushing the top surface of needle guide (6) with pressured fuel to force
said needle valve (1) moving outward, therefore form an annular outlet
(131') between said arrow-head shape needle head and said nozzle body tip
surface (301) to inject fuel in a hollow conical spray pattern.

4. A fuel injector of claim 1, wherein said inward opening needle valve
(2) has a cylindrical space to partially hold spring (5) and said outward
opening needle valve (1), where in said inward opening needle valve (2)
is further comprising a needle guide (203) and fuel passages (232), and a
top end (205) to define the needle lift together with needle guide (6),
and thrusting surfaces (204, 206) to generating lifting force to lift the
needle to inject fuel in conventional multiple jet spray pattern through
fuel outlets (302);

5. A fuel injector of claim 1, where in the half fuel spray angle for
hollow conical spray (al) and half spray angle for multiple jet (a2) can
be same or different, where in with preferred embodiment such that al is
smaller than a2.

6. A fuel injector according to any claims 1 to 5 above, wherein the
maximum needle lift (H) for both outward and inward opening valves (1,2)
is approximately in the range of 0-300 μm, the needle head diameter of
said outward opening needle valve (1) is approximately in the range of
0.8-3.5 mm, and the half conical spray angle (a1) is approximately in the
range of 15-60 degree, and the half multiple jet spray angle (a2) is
approximately in the range of 60-75 degree;

7. A fuel injector according to any of the claims 1 to 6 above, where in
the guiding surface of the inward opening outer needle valve (2) and the
guiding surface of needle guide (6) for said outward opening inner valve
(1) shares a same section of cylindrical inner bore (307) surface of said
nozzle body (3) wherein it has means to ensure the coaxial movement of
said inward and outward opening needle valves (1, 2) along the center
axial line of said nozzle body (3).

8. A fuel injector according to any claim of 1 to 7, wherein it has means
to inject one type of fuel in hollow conical spray pattern through
annular fuel outlets (131') controlled by said outward opening needle
valve (1) and inject another type of fuel through multiple jet fuel
outlets (302) controlled by said inward opening needle valve (2).

9. A fuel injector according to any claim of 1 to 8, wherein it has means
to inject the same fuel with different pressures through annular fuel
outlets (131') controlled by said outward opening needle valve (1) and
multiple jet fuel outlets (302) controlled by said inward opening needle
valve (2), preferably with low pressure fuel supplied to said annular
outlets (131') and high pressure fuel supplied to said multiple jet fuel
outlets (302).

10. An internal combustion engine using at least one fuel injector of any
claim above, which can be a spark-ignition engine or a
compression-ignition engine, where in it has means to inject dual fuels
with different spray patterns at different injection timings, preferably
with a second type of fuel injected in hollow conical spray patterns for
earlier injections which is away from engine top dead center (TDC), and
at least one main fuel injection with a first type of fuel injected in
conventional multiple jets close to TDC, and one optional late injection
which is away from TDC with second type of fuel in hollow conical spray
patterns.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priority
of U.S. Provisional Applications No. 61/393,359 filed on Oct. 15, 2010,
the contents of which are incorporated herein by reference.

TECHNICAL FIELDS

[0002] This invention related to a fuel injector and an internal
combustion engine. More specifically, this invention disclosed a fuel
injector with both inward and outward opening needle valves which can
inject fuel in homogenous hollow conical spray or conventional multiple
jet sprays selectively, and an engine using at least one such fuel
injector, which can be a spark-ignition engine or a compression-ignition
engine.

BACKGROUND OF THE INVENTION

Description of the Related Art

[0003] The combustion process in a conventional direct injection Diesel
engine is characterized by diffusion combustion with a fixed-spray-angle
multi-hole fuel injector. Due to its intrinsic non-homogeneous
characteristics of fuel-air mixture formation, it is often contradictory
to simultaneously reduce soot and NOx formation in a conventional diesel
engine. Over last two decades, significant progress has been made for
Diesel engine combustion (U.S. Pat. Nos. 4,779,587, 6,230,683), but
further reducing emissions from Diesel engines to comply upcoming
emission legislations still remains a challenge. Progress has been made
in recent years for advanced combustion modes, such as Homogeneous-Charge
Compression-Ignition (HCCI) combustion and Premixed Charge Compression
Ignition (PCCI). However, many issues remain to be solved to control the
ignition timing, the duration of combustion, the rate of combustion for
HCCI and PCCI engines for various load conditions. It seems to be a more
viable solution to operate engine in mixed-mode combustion, or in HCCI
mode or partially premixed mode at low to medium loads, and in
conventional diffusion combustion mode at high loads for the near future.
Or, we can use mixed-mode combustion even in same power cycle, such as
proposed by the inventor in U.S. patent application Ser. No. 12/143,759.

[0004] A key challenge for mixed-mode combustion with conventional
fix-angle multi-hole nozzle is surface wetting for early injections.
There are many inventions (for example, PCT/EP2005/054057) could provide
dual spray angle multiple jets spray patterns with smaller angle for
early injections and larger spray angle for main injections. However,
researchers find that, even with smaller jets, the conventional multiple
jets spray still tend to wet the piston top and thus could cause emission
issues such as hydrocarbon and mono-dioxide (SAE paper 2008-01-2400).
This observation especially tends to be true for passenger car engines
where cylinder diameter is small. In contrast, hollow conical sprays tend
to give shorter spray pattern and much finer atomization which
significantly cuts the probability of combustion chamber surface wetting.
On another side, most inventions disclosed so far are using inward
opening for both inner and outer needle valves for producing multiple
jets sprays. Such an arrangement produces significant space accommodation
challenges and practical application issues to ensure the sealing of the
two needle valves since the space inside the nozzle tip is very small.
Thus, most dual needle fuel injector designs, even though they hold
potentials to enable new combustion modes, can not be put into practical
applications so far due to challenges in manufacture and durability
concerns. Changing one needle motion of the dual needle structure to
outward opening will reduce this space limitation on nozzle tip, and can
leverage the space outside the inner space of nozzle tip for sealing
surfaces. At the same time, the outward opening needle valve can produce
more soft and homogeneous hollow conical sprays patterns which are more
desirable for early injection premixed combustion.

[0005] To reduce carbon dioxide emissions, bio-fuels production such as
ethanol and biodiesels have increased. Researchers have found that using
ethanol with diesel fuel can reduce both soot and nitride oxide
emissions. Currently, most dual fuel applications are practiced with one
type of fuel injected in intake ports, another type of fuel injected into
cylinder directly, with a different set of fuel injectors for each fuel.
Injecting both bio-fuel and diesel fuel directly into cylinder with a
single injector capable of dual fuel injection could potentially cut the
complexity and cost of the fuel system, and further leverage the benefits
of different fuel properties for optimizing combustion.

SUMMARY OF THE INVENTION

[0006] This invention disclosed a variable orifice fuel injector with
coaxial inward and outward opening valves to inject fuel in hollow
conical spray patterns and conventional multiple jet spray patterns
selectively and independently. The variable orifice fuel injector can
generate a hollow conical spray with smaller penetration which is
suitable for early premixed combustion, it can also produce conventional
multiple jets for conventional diffusion combustion. The fuel injector
has the capability to quickly switch fuel spray pattern in a same engine
power cycle, and is capable of injecting two different fuels in the same
engine power cycle.

[0007] The current invention uses one inward opening needle valve for
multiple-jet injection and one outward opening needle to provide hollow
conical spray for early or late injections such as for after-treatment
purpose. The seal surface for the outward opening needle valve is outside
the nozzle body tip without competing with the inward opening valve for
inner nozzle tip space. So it can ensure better sealing for both the
inward opening and outward opening needle valves. The currently disclosed
fuel injector can generate a hollow conical fine uniform spray and
multi-jet spray patterns separately and selectively to meet the needs for
variable spray penetration, variable spray angles for different engine
operating conditions. The invention injector can provide an optimized
spray pattern, including variable spray angles, to minimize wall-wetting
and oil dilution related to early and post injections, thus cut
emissions. It provides significant potential for a high efficiency clean
engine with different fuels.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a fragmentary sectional view of a first exemplary
embodiment of an injector of the invention with only key components
marked;

[0009] FIG. 2 is a fragmentary sectional view of a first exemplary
embodiment of an injector of the invention with key components, key fuel
passages, key surfaces, and key pressure control chambers marked.

[0010] FIG. 3 is an illustration of the operation state of injecting
hollow conical spray by the embodiment of the fuel injector illustrated
in FIG. 1;

[0011] FIG. 4 is an illustration of the operation state of injecting
conventional multiple jet sprays by the embodiment of the fuel injector
illustrated in FIG. 1;

[0012] FIG. 5 is an illustration of the injection spray patterns along
with injection timings for an internal combustion engine using the fuel
injector as in FIG. 1;

[0019] 6--needle guide which is tightly couple with needle valve 1 and
can slide inside 3, 601--bottom surface of 6, 681--contact surface
between 6 and 8; part 6 could also hold a check valve to block fuel back
flow from nozzle tip.

[0036] A first embodiment was shown in FIG. 1 to FIG. 4. FIGS. 1 & 2 show
the State I when both the outward opening valve 1 and inward opening
valve 2 is at seating position, no fuel is injected. At State I, the
combined pressure force from pressure control chamber 261' and the
elastic force from spring 5 are urging both needle valves 1 and 2 into
seating positions. While at State I, valve 11 is closed, valve 10 is
open, valve 9 is closed.

[0037] FIG. 3 shows the State II when the outward opening needle valve 1
is open, and a second fuel, such as ethanol or gasoline, is injected into
combustion chamber in a hollow conical spray pattern (20). When control
valve 11 is open, high pressure fuel from 12 will fill the pressure
control chamber of 681'. The pressured top surface of guide 6 is larger
than the pressured bottom surface of guide 6, and the components were
designed (including pressure levels and spring strength) such that when
the control valve 9 is also opened, it will ensure the downward force
applied to 6 will conquer the force from spring 5 and upward force from
bottom of 6. The needle valve 1 will be forced to move outward and form
an annular injection outlet 131', fuel will be guided to nozzle tip
through passage from 803 to 701 to 106, and continue to 105 to 121, and
injected into combustion chamber in a hollow conical spray pattern
through annular outlet 131'. At the same time, due to the fast transient
process and small distance between guide 6 and top of needle 2, the
pressure in 261' is still high enough to conquer the forces lifting
needle valve 2, therefore needle valve 2 remains seated. By the time of
ending injection, control valve 11 is closed, valve 10 is open, control
valve 9 is closed, the pressure will be raised in chamber 261', needle
guide 6 will be pushed back to top position, the needle valve 1 will be
returned to seating position. At the same time, the control valve 9 will
be closed. The pressure will built up in pressure control camber 261' and
urge both needle valve 1 and 2 in seating position, fuel injection ends,
and the fuel injector return to State I.

[0038] FIG. 4 shows the State III when the inward opening needle valve 2
is open, and a first fuel, such as diesel or bio-diesel fuel, is injected
into combustion chamber in conventional multiple jet spray patterns (21).
When control valve 9 is open from State I and valve 11 and 10 keeps the
same states as State I, small amount of high pressure fuel will flow out
from control chamber 261' to low pressure fuel sink 15', the pressure in
control chamber 261' is reduced such that the thrusting force from the
thrusting surface of needle valve 2 will conquer the downward forces from
spring 5, the needle valve 2 will be lifted from its seating position,
the high pressure fuel will pass through passage 303 to 233 and 232 and
flow in one pass 231' under the needle seat of 2 to supply fuel to fuel
outlet 302 to inject fuel into combustion chamber. Once control valve 9
is closed, the pressure in control chamber 261' will rise again, and the
pressure force on top of needle valve 2 will conquer the thrusting forces
on needle valve 2, with addition of pressing force from spring 5, the
needle valve 2 will be forced into seating position, fuel injection ends,
and the injector return to closing position as stated in State I.

[0039] The invention fuel injector can also reach another state--State IV
(not shown), where both the inward opening valve and outward opening
valve is open, dual fuels are injected in both multiple jet spray
patterns and hollow conical spray patterns. Even though this state is
rarely used, but it is doable. To reach State IV from State I, we first
open control valve 9, this will activate the inward needle valve to
inject first fuel in multiple jet format, than we open control valve 11
to open needle valve 1, by adjusting the time delay between turning on
valve 11 and 9, the forces from pressure chamber 681' and 261' and spring
5 will reach a transient balance, a second fuel, partially mixed with
first fuel at nozzle tip, will also be injected from outlet 131' in
hollow conical spray pattern. When we close the control valve 11, the
outward opening valve 1 will return to seating position, when the control
valve 9 is closed, the inward opening valve 2 will be forced into seating
position, all fuel injections ends. The fuel injector returns to State I.

[0040] We have illustrated one embodiment here. For those skilled in the
art, it is easy to give alternatives based on the same operation
mechanism. The embodiment illustrated here should be considered as an
example without limiting the scope of the invention. Other embodiments
with the same key characteristics and spirit are considered under the
scope of this invention. For example, one can add a throttling valve
(10') under control valves (9, 10). One can also add a spring under
throttling valve (10') and above needle guide (6) in the fuel passage
(802) to damp the force of the needle guide (6). As an alternative for
needle clip (7), one can use screw (161') to tight needle valve guide (6)
into the outward opening needle valve (1). Further, we may apply
adiabatic material coating such as ceramics on top surface of needle head
(104) of needle valve (1). For another example, the first fuel and second
fuel are the same fuel, thus the injector becomes a single fuel injector.
Following features are considered as the key characteristics of the
invention.

[0041] Statement A: A variable orifice fuel injector
comprising: a nozzle body (3) comprising passages for pressured fuel, an
inner cylindrical space (307) for receiving two longitudinally
displaceable coaxial needle valves (1,2) with an inner needle valve (1)
which is outward opening and which is moving away relative to said nozzle
body (3) large end (306) to reach opening position, and an outer needle
valve (2) which is inward opening and which is moving toward nozzle body
large end to reach opening position, and a needle valve guide (6) tightly
guide said inner needle valve (1) along cylindrical space of said nozzle
body (3), small cylindrical fuel outlets (302) in said nozzle body (3)
and one annular fuel outlet formed by the gap between said nozzle body
(3) and said outward opening needle valve (1) when it is opened, and two
seal surfaces on said nozzle body (3) with a conical surface (231) which
provides sealing for said inward opening valve (2) to block fuel, and
another surface (131) which provides the sealing for the outward opening
valve (1) and guides the fuel path, a spring (5) partially contained in
said needle valve (2) urging both said two coaxial needle valves (1,2)
into biased seating positions to block fuel, a holding cap (4) to hold
parts, and a valve block (8) to hold control valves, and said outward
opening needle valve (1) has means to inject fuel into combustion chamber
in a hollow conical spray pattern through annular fuel outlet (131') when
it is displaced from seating position by driving forces; and said inward
opening needle valve (2) has means to inject fuel into combustion chamber
in conventional multiple jet patterns through fuel outlets (302) when
said needle valve (2) is lifted; Where in, said outward opening needle
valve (1) and inward opening needle valve (2) has means to inject
different fuels in different hollow conical spray patterns and
conventional multiple jet spray patterns selectively and independently.

[0042] Statement B: A fuel injector according to above Statement A, where
in it is comprising at least two control valves (9, 10, 11) to block and
flow at least one type of fuel from high pressure fuel reservoirs (12,
13) to low pressure fuel sink (15, 15') to produce the lifting and
closing forces on said needle valves (1, 2) through generating pressure
differences in pressure control chambers (381, 681', 261', 234), where in
two of the control valves (10, 11) have opposite opening-closing status
and can be served with a single solenoid or piezoelectric actuator to
control the lifting of said outward opening needle valve (1), and another
valve (9) is served with a separate actuator to control the lifting and
closing of said inward opening valve (2), where in said two valves (1,2)
have the same maximum lift (H).

[0043] Statement C: A fuel injector of according to Statement A, where in
said outward opening needle valve (1) is longitudinally displaceable and
partially within said inward opening needle valve (2) and guided by said
needle guide (6) which is longitudinally displaceable in the inner bore
of said nozzle body (3), and said needle valve (1) has a partially tube
section (106) to supply fuel and a converging-diverging-converging
arrow-head shape needle head for guiding a hollow conical spray of fuel,
wherein said needle valve (1) is at a biased closing position with its
seal surface (102) being pressed against nozzle body (3) by spring (5)
and pressure force on needle guide bottom surface (601) to block fuel
flow, or at an opening position through pushing the top surface of needle
guide (6) with pressured fuel to force said needle valve moving outward,
and inject fuel in a hollow conical spray pattern through annular fuel
outlet (131') between said arrow-head shape needle head and said nozzle
body tip surface (301).

[0044] Statement D: A fuel injector of according to above Statement A,
where in said inward opening needle valve (2) has a cylindrical space to
partially hold spring (5) and said outward opening needle valve (1),
where in said needle valve (2) is further comprising a needle guide (203)
and fuel passages (232), and a top end (205) to define the maximum needle
lift together with needle guide (6), and thrusting surfaces (204, 206) to
generating lifting force to lift the needle to inject fuel in
conventional multiple jet spray pattern through fuel outlets (302);

[0045] Statement E: A fuel injector of according to above Statement A,
where in the half fuel spray angle for hollow conical spray (a1) and half
spray angle for multiple jet (a2) can be same or different, where in with
preferred embodiment such that a1 is smaller than a2.

[0046] Statement F: A fuel injector according to any Statements A to E
above, wherein the needle lift for the opening position is approximately
in the range of 0-300 μm, the needle head diameter of said outward
opening needle valve (1) is approximately in the range of 0.8-3.5 mm, and
the half conical spray angle (a1) is approximately in the range of 15-60
degree, and the half multiple jet spray angle (a2) is approximately in
the range of 60-75 degree;

[0047] Statement G: A fuel injector according to any of the above
Statements A to F, where in the guiding surface of the inward opening
needle valve (2) and the guiding surface of needle guide (6) for said
outward opening valve (1) shares a same section of cylindrical inner
surface of said nozzle body (3) where in it has means to ensure the
coaxial movement of said inward and outward opening needle valves (1, 2)
along the center axial line of said nozzle body (3).

[0048] Statement H: A fuel injector according to any of above Statements A
to G, wherein it has means to inject one type of fuel in hollow conical
spray pattern through annular fuel outlets (131') controlled by said
outward opening needle valve (1) and inject another type of fuel through
multiple jet fuel outlets (302) controlled by said inward opening needle
valve (2). The fuels at the two fuel supply pressure reservoirs (12, 13)
are different type of fuels, for example, ethanol and diesel in (12) and
(13), respectively.

[0049] Statement I: A fuel injector according to any of above Statements A
to H, wherein it has means to inject the same fuel with different
pressures through annular fuel outlets (131') controlled by said outward
opening needle valve (1) and multiple jet fuel outlets (302) controlled
by said inward opening needle valve (2), preferably with low pressure
fuel supplied to said annular outlets (131') and high pressure fuel
supplied to said multiple jet fuel outlets (302). The fuels at the two
fuel supply pressure reservoirs (12, 13) are same type of fuel but with
different pressure, for example, low pressure fuel in reservoir (12) and
high pressure fuel in reservoir (13), respectively.

[0050] Statement J: An internal combustion engine using a fuel injector of
any of above Statements A to I, which can be a spark-ignition engine or a
compression-ignition engine, where in it has means to inject dual fuels
with different spray patterns at different injection timings, preferably
with a second type of fuel injected in hollow conical spray patterns for
earlier injections which is away from engine top dead center (TDC), and
at least one main fuel injection with first type of fuel injected in
conventional multiple jets around TDC, and one optional late injection
which is away from TDC with second type of fuel in hollow conical spray
patterns.